Science magazine reports the discovery of quantum Griffiths singularity of
superconductor-metal transition in Ga thin films
Time：2015-10-27ClickTimes：
More than 40 years ago, Robert B. Griffiths predicted that phase transitions
can be dramatically changed by disorder effect and in particular the dynamical
critical exponent can diverge. In the last 40 years, this theory has been
applied to quantum phase transitions and developed into the theory of “quantum
Griffiths singularity”. However, the major signature of the theory, the
divergence of dynamical critical exponent, is very difficult to observe in
experiments.
Recently, Prof. Jian Wang, in collaboration with Prof. Xincheng Xie, Prof. Xi
Lin, and Prof. Fa Wang at Peking University, as well as Prof. Qi-Kun Xue and
Prof. Xu-Cun Ma at Tsinghua University, observed for the first time the quantum
Griffiths singularity in two dimensional (2D) superconducting system. They
studied three monolayer thick Ga films in ultralow temperature regime, in which
2D superconductivity and superconductor to metal transition were detected.
Furthermore, when approaching the zero temperature quantum critical point, they
found the divergence of the dynamical critical exponent, which is consistent
with the Griffiths singularity behavior. The superconductor-metal quantum phase
transition in this 2D superconducting system with disorder could thus be
explained by the theory of quantum Griffiths singularity, which is different
with the previous understanding of quantum phase transition in 2D
superconductors.
The paper was selected by Science Express and online published in Science on
October 15, 2015 (DOI: 10.1126/science.aaa7154): http://www.sciencemag.org/content/early/2015/10/14/science.aaa7154.full.
Prof. Jian Wang, Prof. Xi Lin at Peking University and Prof. Xu-Cun Ma at
Tsinghua University are corresponding authors of this paper. Ying Xing, Hai-Long
Fu, Dr. Haiwen Liu at Peking University and Hui-Min Zhang at Institute of
Physics, Chinese Academy of Sciences contributed equally to this work.
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Figure: The superconductivity in 3 monolayer thick Ga
film and the divergence of the critical exponent approaching the quantum
critical point (zero temperature limit).
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The work was supported by National Basic Research Programs of China, National
Natural Science Foundation of China, 1000 Talents Program for Young Scientists
of China, the Research Fund for the Doctoral Program of Higher Education (RFDP)
of China, and Collaborative Innovation Center of Quantum Matter, China.
